Balloon Flight Engineering Model Balloon Flight Results

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Balloon Flight Engineering Model Balloon Flight
Results
LAT - Balloon Flight Team GSFC, SLAC, SU,
Hiroshima, NRL, UCSC, Pisa (Led by D. Thompson,
G. Godfrey, S. Williams) T. Kamae on behalf of
the GLAST/LAT Collaboration

• CONTENTS
• Rationale and Goals
• Preparation
• Balloon Flight and Operations
• Instrument Performance
• Results VS. Geant4
• Lessons Learned
• Conclusions

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Rationale Why a Balloon Flight?
NASA Announcement of Opportunity "The LAT
proposer must also demonstrate by a balloon
flight of a representative model of the flight
instrument or by some other effective means the
ability of the proposed instrument to reject
adequately the harsh background of a realistic
space environment. A software simulation is not
deemed adequate for this purpose. Planning the
balloon flight Identify specific goals that
were practical to achieve with limited resources
(time, money, and people), using the
previously-tested Beam Test Engineering Model
(BTEM) as a starting point.
Fig.1 Beam Test Engineering Model (99) (BTEM),
a prototype GLAST/LAT tower. The black box to
the right is the anticoincidence detector (ACD),
which surrounds the tracker (TKR). The
aluminum-covered block in the middle is the
calorimeter (CAL). Readout electronics were
housed in the crates to the left.
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Goals of the Balloon Flight

• Validate the basic LAT design at the single tower
  level.
• Show the ability to take data in the high
  isotropic background flux of energetic particles
  in the balloon environment.
• Record all or partial particle incidences in an
  unbiased way that can be used as a background
  event data base.
• Find an efficient data analysis chain that meets
  the requirement for the future Instrument
  Operation Center of GLAST.

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PreparationWhat Was Needed for this Balloon
Flight?

• A LAT detector, as similar as possible to one
  tower of the flight instrument - functionally
  equivalent. BTEM
• Rework on Tower Electronics Module. Stanford U
• Rework on Tracker. UCSC
• Rework on Calorimeter. NRL
• Rework on ACD. GSFC
• External Gamma-ray Target (XGT). Hiroshima, SLAC
• On-board software. SLAC, SU, NRL
• Mechanical structure to support the instrument
  through launch, flight, and recovery. GSFC, SLAC
• Power, commanding, and telemetry. NSBF, SU,
  SLAC, NRL
• Real-time commanding and data displays. SU,
  SLAC, NRL
• Data analysis tools. SLAC, GSFC, UW, Pisa
• Modeling of the instrument response. Hiroshima,
  SLAC, KTH

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Preparation BFEM Integration at SLAC
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Preparation BFEM Transportation to Goddard
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Preparation Pre-shipment Review on July 16, 2001
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Preparation Pre-Launch Review
Real-time event display. A penetrating cosmic
ray is seen in all the detectors.
Pre-launch testing at National Scientific Balloon
Facility, Palestine, Texas. August, 2001.
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Balloon Team at Palestine Texas
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Flight and Operation Launch on August 4, 2001
First results (real-time data) trigger rate as a
function of atmospheric depth. The trigger rate
never exceeded 1.5 KHz, well below the BFEM
capability of 6 KHz.
The balloon reached an altitude of 38 km and gave
a float time of three hours.
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Flight and Operation Onboard DAQ and Ground
Electronics Worked
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Flight and Operation Onboard DAQ and Ground
Electronics Worked
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Instrument Performance All Subsystems Performed
Properly
External Targets (4 plastic scint) to test
direction determination and measure interaction
rate.
4 million L1T in 1 hour level flight and 100k
events down linked. Many more in ascending part
of flight and in HD.
ACD (13 scint. tiles) to detect charged particles
and heavy ions (Zgt2).
Tracker (26 layers of SSD) to measure charged
tracks 200um and reconstruct gamma ray direction.
CAL (CsI logs) To image EM energy deposition.
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Instrument Performance All Subsystems Performed
Properly
Level-1 Trigger Rate (L1T)
Level Flight Data Geant4

(Default Cosmic-Ray Fluxes) All
500/sec
504/sec Charged 444/sec
447/sec Neutral 56/sec
57/sec
Number of Events Recorded
Events through Downlink Events in Hard
Disk Ascending 30.5k (R53) 109k
(R54) 1.5M (R53R54) Level Flight
105k (R55)
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Instrument Performance ACD Threshold and
Efficiency
Anti-Coincidence Detector Pulse height distr. for
stiff charged particles shows clean separation of
the peak from noise. Scinti. Eff. gt 99.96 if
cracks are filled with scintillator tapes.
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Instrument Performance CALs Energy Measurement
and Imaging
Imaging capability demonstrated
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Instrument Performance CPU Reboot and DAQ
Livetime
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Instrument Performance Dead Time of DAQ as
Predicted
68us
Will be 20us in LAT
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Instrument Performance Tracker and XGT
Association
Cosmic ray interaction in 4 External Targets
(plastic scintilators)
Hadronic shower produced in XGT (416 recorded)
Gamma ray produced in XGT (20 identified)
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Instrument Performance Mechanical Stability
Proven
BFEM has experienced 7g shocks
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Instrument Performance Mechanical Stability
Proven
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Results Reconstruction of Events
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Results VS Geant4 Simulation of Cosmic Ray Events
Proton spectrum
e-/e spectra
gamma spectrum
e-/e
Gammas prod. by cosmic protons in the atmosphere
Primary protons passing into the Earth magnetic
field and secondary protons prod. by
primary protons in the atmosphere
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Results VS Geant4 Charged Particles Flux and
Angular Distribution
Default fluxes and angular distributions
protons, muons, and electrons
Data is higher than the model flux!
g
e-/e
Geant4 prediction
muons
protons
Cosine of cosmic-ray direction
Downward
90 deg.
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Results VS Geant4 Charged Particle
Distribution
Charged particle hit distribution default
fluxes and angular distributions
Data is higher than the model flux near the
Calorimeter
Data
Geant4 prediction
Top of Tracker
Calorimeter side
Tracker layer number
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Results VS Geant4 Neutral Particle Distribution
Neutral particle hit distribution gammas and
under-the-ACD electrons
Geant4 prediction
Data is higher than the model flux above the
Super GLAST layers
Data
Top of Tracker
Calorimeter side
Tracker layer number
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Lessons Learned

• Test instrument in the flight environment as much
  as possible
• Leak in the pressure vessel (Was very expensive
  for BFEM)
• Two (xy) layer sets left out of L1T (Little
  side-entering muons on ground)
• Importance of a well-tune Instrument and CR
  Simulator
• A strong team assigned for LAT simulation
• Simulators for every steps of Integration and
  Testing
• Detection of a small delicate fault in L1T after
  tuning the Geant4 simulator
• Constant monitoring of the LAT DAQ and filtering
  process

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Conclusions

• Goals of the balloon flight were achieved.
• BFEM successfully collected data using a simple
  three-in-a-row trigger at a rate that causes
• little concern when extrapolated to the full
  flight unit LAT.
• There seems little doubt that gamma-ray data can
  be extracted from the triggers and that the
  background can be rejected at an acceptable
  level.
• Through the data analysis, we gained confidence
  in our ability to simulate the instrument and
• the cosmic ray background.
•  
• Balloon flight offered a first opportunity for
  the LAT team to deal with many of the issues
• involved in a flight program.
• Lessons learned drawn from BFEM experiences will
  be fed back to the enitre LAT team and
• that will make the flight unit development
  slightly easier.

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Who Was Involved in this Balloon Flight?

• D. J. Thompson, R. C. Hartman, H. Kelly, T.
  Kotani, J. Krizmanic, A. Moiseev, J. F. Ormes, S.
  Ritz, R. Schaefer, D. Sheppard, S. Singh, NASA
  Goddard Space Flight Center
• G. Godfrey, E. do Couto e Silva, R. Dubois, B.
  Giebels, G. Haller, T. Handa, T. Kamae, A.
  Kavelaars, T. Linder, M. Ozaki1, L. S. Rochester,
  F. M. Roterman, J. J. Russell, M. Sjogren2, T.
  Usher, P. Valtersson2, A. P. Waite, Stanford
  Linear Accelerator Center (KTH, ISAS)
• S. M. Williams, D. Lauben, P. Michelson, P.L.
  Nolan, J. Wallace, Stanford University
• T. Mizuno, Y. Fukazawa, K. Hirano, H. Mizushima,
  S. Ogata, Hiroshima University
• J. E. Grove, J. Ampe3, W. N. Johnson, M.
  Lovellette, B. Phlips, D. Wood, Naval Research
  Laboratory
• H. f.-W. Sadrozinski, Stuart Briber4, James
  Dann5, M. Hirayama, R. P. Johnson, Steve
  Kliewer6, W. Kroger, Joe Manildi7,G. Paliaga, W.
  A. Rowe, T. Schalk, A. Webster, University of
  California, Santa Cruz
• M. Kuss, N. Lumb, G. Spandre, INFN-Pisa and
  University of Pisa

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Good Teamwork was the Key for our Success
Integration
Command and Data Flow Responsibilities
Payload Responsibilities